In the prior art, 3D printing systems generally include a robot and a print head mounted on an end of the robot. Materials are sprayed or deposited from the print head onto a positioning platform, forming a product having a desired shape on the positioning platform as the robot moves the print head based on a predetermined route. 3D printing is thus fundamentally different from conventional machining; in 3D printing, a desired shape is created by adding materials instead of removing materials as in machining.
In the prior art, the robot for manipulating the print head can only move in X, Y and Z directions perpendicular to each other and the positioning platform for supporting the product made from the materials is stationary. Additionally, the product to be printed is divided into a plurality of two-dimensional (2D) horizontal layers in the Z direction. The robot manipulates the printing head to move in a horizontal plane defined by X and Y to print the plurality of 2D horizontal layers successively. The end product is created by successively overlaying the plurality of 2D horizontal layers in the Z direction.
Since such existing 3D printing systems only move in X, Y and Z directions perpendicular to each other, only the position of the print head may be adjusted with respect to the positioning platform. The angle of the print head with respect to the positioning platform cannot be adjusted. Therefore, in such existing 3D printing systems, the print head only can be moved over a 2D plane or a 2D curve, rather than a 3D curved surface or a 3D curve, thus limiting its usage.